The present invention relates to a unit for dewatering dredged or slurried material. More particularly, the present invention relates to a vibrating screen unit for dewatering dredged or slurried material which incorporates a dual deck screen system.
Dredges dig and remove material, such as sand and gravel, from the bottom of bodies of water, such as lakes and rivers. The primary means for dewatering dredged or slurried material is typically a vibrating screen unit having a deck surface covered by a screen mesh media which has a matrix of openings of a predetermined size and arrangement. Unlike conventional vibrating screen applications where material separation is achieved by having as much material as possible of a size less than that of the openings in the screen media fall through the screen deck surface, dewatering of material is achieved by retaining as much of the material less than the size of the openings as possible on the screen deck surface while passing the water through the openings. During dewatering, a small amount of fine grit passes through the openings in the screen mesh media while the dewatered material is discharged onto a conveyor belt for processing at a discharge end of the unit.
In general, for a particular feed material, the dewatering efficiency of vibrating screen units is dependent on the size or surface area of the screen deck. Capacity can be increased by enlarging the screen deck of vibrating screen units and increasing the feed rate of slurry. However, the economics of sizing up vibrating screen units to increase capacity can be significant and even cost prohibitive.
The present invention provides vibrating screen units which have increased dewatering efficiencies for given overall sizes.
The present invention provides a vibrating screen unit for dewatering material which unit has a greater dewatering capacity than similar sized units.
The vibrating screen unit of the present invention includes upper and lower screen decks and is designed to allow excess water discharged from the upper screen deck to enter between the upper and lower screen decks.
The vibrating screen unit of the present invention includes a discharge lip on the upper screen unit which creates interruptions or gaps in the material that is discharged from the upper screen deck onto the lower screen deck. These interruptions or gaps provide passageways for excess water to flow backwards onto the lower screen deck and beneath the upper screen deck.
The present invention provides a vibrating screen unit for dewatering material which includes:
a frame;
a lower screen deck coupled to the frame;
an upper screen deck coupled to the frame; and
a jagged discharge lip provided at a downstream end of the upper screen deck which jagged discharge lip interrupts the flow of solids which is discharged from the upper screen deck onto the lower screen deck.
The present invention further provides a vibrating screen unit for dewatering material which includes:
a frame;
a lower screen deck coupled to the frame having a feed end and a discharge end;
an upper screen deck coupled to the frame and having a feed end and a discharge end; and
means to incline each of the upper and lower screen decks so that their respective discharge ends are elevated above their respective feed ends.
The present invention also provides a method of dewatering material which involves:
providing a vibrating dewatering unit having a lower screen deck and an upper screen deck which is positioned above a portion of the lower screen deck;
feeding a material to be dewatered onto the upper screen deck;
discharging the material from the upper screen deck onto the lower screen deck so that solids therein are directed toward a discharge end of the lower screen deck and a liquid therein is directed in an opposite direction beneath the upper screen deck.